41 research outputs found
Quantum Computational Gates with Radiation Free Couplings
We examine a generic three state mechanism which realizes all fundamental
single and double qubit quantum logic gates operating under the effect of
adiabatically controllable static (radiation free) bias couplings between the
states. At the instant of time that the gate operations are defined the third
level is unoccupied which, in a certain sense, derives analogy with the
recently suggested dissipation free qubit subspaces. The physical
implementation of the mechanism is tentatively suggested in a form of the
Aharonov-Bohm persistent current loop in crossed electric and magnetic fields,
with the output of the loop read out by a (quantum) Hall effect aided
mechanism.Comment: 21 pages including 7 figures, revte
The Moyal-Lie Theory of Phase Space Quantum Mechanics
A Lie algebraic approach to the unitary transformations in Weyl quantization
is discussed. This approach, being formally equivalent to the
-quantization, is an extension of the classical Poisson-Lie formalism
which can be used as an efficient tool in the quantum phase space
transformation theory.Comment: 15 pages, no figures, to appear in J. Phys. A (2001
The effect of sample properties on the electron velocity in quantum Hall bars
We report on our theoretical investigation of the effects of the confining
potential profile and sample size on the electron velocity distribution in
(narrow) quantum-Hall systems. The electrostatic properties of the electron
system are obtained by the Thomas-Fermi-Poisson nonlinear screening theory. The
electron velocity distribution as a function of the lateral coordinate is
obtained from the slope of the screened potential at the Fermi level and within
the incompressible strips (ISs). We compare our findings with the recent
experiments.Comment: 8 pages, 6 figure
A measurable force driven by an excitonic condensate
Cataloged from PDF version of article.Free energy signatures related to the measurement of an emergent force (approximate to 10(-9)N) due to the exciton condensate (EC) in Double Quantum Wells are predicted and experiments are proposed to measure the effects. The EC-force is attractive and reminiscent of the Casimir force between two perfect metallic plates, but also distinctively different from it by its driving mechanism and dependence on the parameters of the condensate. The proposed experiments are based on a recent experimental work on a driven micromechanical oscillator. Conclusive observations of EC in recent experiments also provide a strong promise for the observation of the EC-force. (C) 2014 AIP Publishing LLC
Robust ground state and artificial gauge in DQW exciton condensates under weak magnetic field
Cataloged from PDF version of article.An exciton condensate is a vast playground in studying a number of symmetries that are of high interest in the recent developments in topological condensed matter physics. In double quantum wells (DQWs) they pose highly nonconventional properties due to the pairing of non-identical fermions with a spin dependent order parameter. Here, we demonstrate a new feature in these systems: the robustness of the ground state to weak external magnetic field and the appearance of the artificial spinor gauge fields beyond a critical field strength where negative energy pair-breaking quasi particle excitations, i.e. de-excitation pockets (DX-pockets), are created in certain k regions. The DX-pockets are the Kramers symmetry broken analogs of the negative energy pockets examined in the 1960s by Sarma. They respect a disk or a shell-topology in k-space or a mixture between them depending on the magnetic field strength and the electron-hole density mismatch. The Berry connection between the artificial spinor gauge field and the TKNN number is made. This field describes a collection of pure spin vortices in real space when the magnetic field has only inplane components. (C) 2014 Elsevier B.V. All rights reserved
Nonlocal, noncommutative picture in quantum mechanics and distinguished canonical maps
Classical nonlinear canonical (Poisson) maps have a distinguished role in
quantum mechanics. They act unitarily on the quantum phase space and generate
-independent quantum canonical maps. It is shown that such maps act in
the noncommutative phase space as dictated by the classical covariance. A
crucial observation made is that under the classical covariance the local
quantum mechanical picture can become nonlocal in the Hilbert space. This
nonlocal picture is made equivalent by the Weyl map to a noncommutative picture
in the phase space formulation of the theory. The connection between the
entanglement and nonlocality of the representation is explored and specific
examples of the generation of entanglement are provided by using such concepts
as the generalized Bell states. That the results have direct application in
generating vacuum soliton configurations in the recently popular scalar field
theories of noncommutative coordinates is also demonstrated.Comment: 14 pages, one figur